Load monitoring systems and methods

ABSTRACT

A system ( 200 ) monitors a load associated with a load carrying member. The system ( 200 ) may include a voltage divider ( 240 ) and a computer device ( 250 ). The voltage divider ( 240 ) measures inductance associated with load sensing elements ( 210 ) that monitor the load carrying member. The computer device ( 250 ) determines displacements of the load sensing elements ( 210 ) based on the inductance associated with the load sensing elements ( 210 ) and determines the load associated with the load carrying member based on the displacements of the load sensing elements ( 210 ). The system may be designed to be portable and/or DC powered.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/228,669, filed on Aug. 26, 2002, the specification of which isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to load monitoring and, moreparticularly, to systems and methods for signal conditioning andprocessing of load monitoring signals

2. Description of Related Art

Load and tension monitoring of load carrying members are very importantin some applications. For example, load and tension monitoring ofmoorings and risers is important in offshore oil production platforms.One such monitoring system includes variable reluctance sensors placedaround the periphery of a load carrying member to measure the loadassociated with that member. This system uses a resonant circuit toprocess signals from the sensors and report results to a marinemonitoring system.

The electronics used in such a system are sophisticated and expensive.The electronics are typically housed in a fixed cabinet and powered byan AC line voltage. Therefore, the electronics are rendered inoperablein the event of line voltage failure, which may occur in criticalsituations, such as in a severe storm.

As a result, there is a need for a monitoring system that isinexpensive, portable, and/or capable of being powered by DC power.

SUMMARY OF THE INVENTION

Systems and methods consistent with the present invention address thisand other needs by providing a monitoring system that is inexpensive,portable, and/or capable of being powered by DC power.

In accordance with the principles of the invention as embodied andbroadly described herein, a system monitors a load associated with aload carrying member. The system may include a voltage divider and acomputer device. The voltage divider measures inductance associated withload sensing elements that monitor the load carrying member. Thecomputer device determines displacements of the load sensing elementsbased on the inductance associated with the load sensing elements anddetermines the load associated with the load carrying member based onthe displacements of the load sensing elements.

In another aspect of the invention, a portable load monitoring systemmonitors the load associated with a load carrying member. The systemincludes a voltage divider and a portable computer device. The voltagedivider is configured to measure inductance associated with load sensingelements that are associated with the load carrying member. The portablecomputer device is configured to determine displacements of the loadsensing elements due to the load based on the inductance associated withthe load sensing elements, and determine the load associated with theload carrying member based on the displacements of the load sensingelements.

In a further aspect of the invention, a system monitors a loadassociated with a load carrying member. The system includes a voltagedivider and a computer device connected to a DC power source. Thevoltage divider is configured to measure inductance associated with loadsensing elements associated with the load carrying member. The computerdevice is configured to determine displacements of the load sensingelements due to the load based on the inductance associated with theload sensing elements, and determine the load associated with the loadcarrying member based on the displacements of the load sensing elements.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate the invention and, together withthe description, explain the invention. In the drawings,

FIG. 1 is an exemplary diagram of an environment in which systems andmethods consistent with the present invention may be implemented;

FIG. 2 is an exemplary diagram of a system in which systems and methodsconsistent with the present invention may be implemented;

FIG. 3 is an exemplary diagram of the load measurement unit of FIG. 2according to an implementation consistent with the present invention;

FIG. 4 is an exemplary diagram of the upper sensor ring of FIG. 3according to an implementation consistent with the present invention;

FIG. 5 is an exemplary diagram of a sensor of FIG. 4 according to animplementation consistent with the present invention;

FIG. 6 is an exemplary detailed diagram of the signal conditioningsystem of FIG. 2 according to an implementation consistent with thepresent invention;

FIG. 7 is an exemplary diagram of a sensor plane that may be constructedto facilitate determination of displacement according to animplementation consistent with the principles of the invention;

FIG. 8 is a flowchart of exemplary processing for determining tension,bending, and orientation of bending associated with a load carryingmember according to an implementation consistent with the presentinvention; and

FIG. 9 is an exemplary diagram of a sensor according to anotherimplementation consistent with the principles of the invention.

DETAILED DESCRIPTION

The following detailed description of the invention refers to theaccompanying drawings. The same reference numbers in different drawingsmay identify the same or similar elements. Also, the following detaileddescription does not limit the invention. Instead, the scope of theinvention is defined by the appended claims and equivalents.

Systems and methods consistent with the present invention provide loadmonitoring that may be used to monitor the load associated with loadcarrying members, such as moorings and risers of offshore oil productionplatforms. The systems and methods may include inexpensive circuitrywith DC power capability. In certain critical situations, such as in asevere storm, uncertainty in the determination of the load associatedwith a load carrying member may be unacceptable. The DC power capabilitypermits the monitoring to occur in situations, such as where there is ACline voltage failure.

The systems and methods consistent with the present invention alsoprovide a portable, compact configuration for deployment to remotelocations. Field personnel can use the portable configuration as adiagnostic and/or troubleshooting tool to quickly localize problems atvarious points in the cabling. In other implementations, the portableconfiguration may be enclosed in a protective container and deployed forload measurements at locations, such as in underwater mooring and risersystems at or near the sea floor.

Exemplary Environment

FIG. 1 is an exemplary environment 100 in which systems and methodsconsistent with the principles of the invention may be implemented. Asshown in FIG. 1, environment 100 may be associated with a floatingproduction system, such as a floating offshore oil platform 110.Platform 110 may be secured to the sea floor via chains or tendons, suchas moorings 120. Oil, gas, and/or water may be extracted and provided toplatform 110 and/or exported via one or more tubes, such as riser 130.It may be important to monitor the load and tension associated withmoorings 120 and riser 130 to make sure that moorings 120 and riser 130are not loose or overstrained, possibly, to the point of breakage, andthat platform 110 is stable.

While systems and methods consistent with the principles of theinvention will be described within environment 100, such systems andmethods are not so limited. In fact, systems and methods consistent withthe present invention may be used in any environment where it may beuseful to monitor the load of a load carrying member.

Exemplary Load Measurement Unit Configuration

FIG. 2 is an exemplary diagram of a system 200 in which systems andmethods consistent with the principles of the invention may beimplemented. System 200 includes one or more load measurement units 210,one or more cables 220, junction box 230, signal conditioning system240, and computer system 250. Computer system 250 and/or signalconditioning system 240 may be powered by AC power or DC power, such asa battery (not shown). The DC power permits computer system 250 and/orsignal conditioning system 240 to operate in the event of AC powerfailure.

Generally, load measurement unit 210 may generate signals indicative ofdisplacement associated with a tendon or tube, such as mooring 120 orriser 130. Cable 220 may connect load measurement unit 210 to junctionbox 230 within platform 110. Cable 220 may include one or moreunderwater connectors. Junction box 230 may provide connection pointsbetween one or more load measurement units 210 and signal conditioningsystem 240. A typical platform 110 may include one or more junctionboxes 230.

Signal conditioning system 240 may gather data for determininginductance associated with load measurement unit 210 based on thesignals from load measurement unit 210. Computer system 250 maydetermine the inductance associated with a load measurement unit 210and, from this, the load associated with mooring 120 or riser 130. Forexample, computer system 250 may determine tension, bending, andorientation of bending associated with mooring 120 or riser 130.

These components will now be described in more detail.

Load Measurement Unit

FIG. 3 is an exemplary diagram of load measurement unit 210 according toan implementation consistent with the principles of the invention. Loadmeasurement unit 210 may be located on a load carrying member, such asmooring 120 or riser 130, approximately 100 or more feet underwater.Load measurement unit 210 may include upper sensor ring 310 and lowersensor ring 320 that form rings around the periphery of the loadcarrying member. Load measurement unit 210 may generate signalsindicative of the displacement between upper sensor ring 310 and lowersensor ring 320.

FIG. 4 is an exemplary diagram of upper sensor ring 310 according to animplementation consistent with the principles of the invention. Sensorring 310 may include approximately three to twelve load sensingelements, such as sensors 410, located around the periphery of the loadcarrying member (e.g., mooring 120 or riser 130). The actual number ofsensors 410 included may be a number sufficient to obtain good estimatesof tension, bending, and the orientation of the bending of the loadcarrying member.

FIG. 5 is an exemplary diagram of a section of sensor 410 according toan implementation consistent with the principles of the invention.Sensor 410 may include a variable reluctance sensor or capacitivesensor. Sensor 410 may include C-shaped magnetic core 510, I-shapedmagnetic core 520, brackets 530 and 540, and windings 550. C-shapedmagnetic core 510 may be constructed, for example, of a highly permeablelaminated transformer material. C-shaped core 510 may be mounted onupper sensor ring 310 via bracket 530 with the ends of the C-shapepointed downward or in a direction generally parallel to the directionof force within the load carrying member.

I-shaped magnetic core 520 may be constructed, for example, of a highlypermeable laminated transformer material. I-shaped magnetic core 520 maybe mounted on lower sensor ring 320 via bracket 540. I-shaped core 520may be positioned so that narrow gaps exist between each end of C-shapedcore 510 and a facing portion of I-shaped core 520. In an implementationconsistent with the principles of the invention, the widths of the gapsare small as compared with any transverse dimension of the ends ofC-shaped core 510. Further, the cross-sectional dimensions or areas ofthe ends of C-shaped core 510 may be smaller than those of the facingportion of I-shaped core 520.

A winding 550 may be mounted around each end of C-shaped core 510closely adjacent to the respective gap. Windings 550 may connect inseries so that their electromotive forces add. As will be understood bythose skilled in the art, C-shaped core 510 and I-shaped core 520 may behighly permeable and, thus, the gaps between cores 510 and 520 mayconstitute most of the reluctance in the magnetic circuit linkingwindings 550. Thus, the inductance exhibited may be directly dependenton the widths of the gaps in the direction of the magnetic flux in thegaps (i.e., the vertical direction in FIG. 5).

As an axial load is applied to sensor 410, the width of the respectivegap between each end of C-shaped core 510 and the adjacent portion ofI-shaped core 520 increases or reduces. As the gaps are reduced, theinductance exhibited increases.

Both of the gaps may be used in determining the value of inductance. Asa result, small increases in the length of one gap can compensate oroffset for small decreases in the length of the other gap. Accordingly,sensor 410 may be relatively insensitive to bending moments appliedthereto (i.e., around a horizontal axis perpendicular to the paper asillustrated in FIG. 5). Bending moments around the orthogonal horizontalaxis lying in the plane of the paper only produce changes in width as afunction of displacement across the surfaces of the ends of both gapsbut not changes in the average width of each gap, to a first orderapproximation.

Cable

Cable 220 may include a marine cable that connects load measurement unit210 to junction box 230 within platform 110. Cable 220 may includeconductors that connect to sensors 410 of load measurement unit 210.Cable 220 may also include one or more underwater connectors with activeor inactive components to relay signals between segments of cable 220.

Junction Box

Junction box 230 may include a set of connection points that connectcables 220 to signal conditioning system 240. One or more junction boxes230 may be located within platform 110. For example, one junction box230 may be located in the control room of platform 110 and anotherjunction box 230 may be located in the lower regions of platform 110,such as where cables 220 come into platform 110.

Signal Conditioning System

FIG. 6 is an exemplary diagram of signal conditioning system 240according to an implementation consistent with the principles of theinvention. Signal conditioning system 240 may gather data fordetermining the inductance and the operational status of sensors 410 andcommunicate this data to computer system 250.

Signal conditioning system 240 may include interface 610, filters 620,driver 630, resistors 640, and switches 650. Interface 610 is shown as acomponent of signal conditioning system 240. In an alternateimplementation, interface 610 may be part of computer system 250.

Interface 610 may include a Personal Computer Memory Card InternationalAssociation (PCMCIA) interface that facilitates the connection of signalconditioning system 240 to computer system 250. Interface 610 mayinclude one or more digital-to-analog (D/A) channels that may be used tooperate components of signal conditioning system 240. If interface 610includes more than one D/A channel, each D/A channel may correspond to adifferent one of sensors 410.

Interface 610 may also include one or more analog-to-digital (A/D)channels that may be used to capture data, such as data used indetermining the inductance of a sensor 410. In the example of FIG. 6,interface 610 includes N+1 A/D channels that correspond to N differentones of sensors 410. A/D channel 0 may be used for calibrations and dataacquisition, as will be described in more detail below. Interface 610may also include ground (GND) connections.

Filters 620 may include conventional low pass filters that are designedto remove noise and aliased components of the signal. Driver 630 mayinclude a sensor line driver that drive signals from the D/A channel.

Resistors 640 may be reference resistors (RR) having a known resistance.Switches 650 may include calibration switches that are used to switchthe components of signal conditioning system 240 between calibration anddata acquisition modes. As shown in FIG. 6, switches 650 may be in theup position during the calibration mode.

Signal conditioning system 240 may view sensor 410 and cable 220 as acombination of resistors, capacitors, and inductors. For example, cable220 may be represented by a capacitor CC, a resistor RC, and an inductorLC. The features of cable 220 may be measured and remain constant.Therefore, the capacitance, resistance, and inductance of cable 220 areknown. Sensor 410 may be represented by a resistor RS and an inductorLS. The resistance of sensor 410 may be measured and remain constant.The inductance of sensor 410 is a variable inductance that changes basedon changes in displacement, as described above. The impedance of cable220 and sensor 410 may be represented by ZSC.

Signal conditioning system 420 uses a voltage divider circuit made up ofthe resistor RR and impedance ZSC to gather data for determining theinductance of sensor 410. The transfer function TF of the voltagedivider may be represented by:${{{TF} \equiv \frac{Vm}{Vi}} = \frac{Z_{SC}}{R_{R} + Z_{SC}}},$where Vi refers to a reference voltage input and Vm refers to a responsevoltage sample. The sensor and cable impedance ZSC may be representedby:${Z_{SC} = \frac{Z_{CC}\left( {R_{C} + Z_{LC} + R_{S} + Z_{LS}} \right)}{Z_{CC} + R_{C} + Z_{LC} + R_{S} + Z_{LS}}},$where ZCC refers to the impedance of the capacitance of cable capacitorCC, ZLC refers to the impedance of cable inductor LC, and ZLS refers tothe impedance of sensor inductor LS. From these equations, the impedanceof inductor LS (ZLS) can be determined. The inductance of inductor LSmay then be determined from the following:$L_{S} = {{{\left( {\frac{R_{R}}{\left( {{1/{TF}} - 1} \right) - {R_{R}/Z_{CC}}} - R_{C} - R_{S}} \right)/j}\quad\omega} - {L_{C}.}}$

Signal conditioning system 240 provides the measurements used indetermining the transfer function TF in the above equation to computersystem 250 via the appropriate one(s) of the A/D channels.

Computer System

Computer system 250 may include a computer device, such as a personalcomputer, laptop, personal digital assistant, etc. To make system 200portable, computer system 250 may include a portable device, such as alaptop or a personal digital assistant. Computer system 250 maydetermine inductance, displacement, and load associated with a loadcarrying member, such as mooring 120 or riser 130. Computer system 250may determine displacement at a number of different locations around theperiphery of the load carrying member. Computer system 250 may convertdetermined sensor inductance values to displacement due to tension anddisplacement due to bending.

Computer system 250 may calibrate the components of signal conditioningsystem 240 in the calibration mode. For example, switches 650 and theA/D channels may be placed into the calibration mode. Computer system250 may output a reference signal via the D/A channel. Computer system250 may then determine magnitude and phase corrections for all channelsrelative to the reference A/D channel 0.

Thereafter, during the data acquisition mode, computer system 250 mayobtain the measurements for determining the transfer functions for thevoltage dividers from signal conditioning system 240. Computer system240 may use the transfer functions to determine the inductance ofsensors 410. For a given inductance value, computer system 240 mayestimate the corresponding displacement for sensor 410 based on priorcalibrations of that sensor 410.

Computer system 250 may then determine displacement due to tension anddisplacement due to bending. FIG. 7 is an exemplary diagram of a sensorplane that may be constructed to facilitate determination ofdisplacement according to an implementation consistent with theprinciples of the invention.

Computer system 250 may determine the displacement of each sensor 410based on its inductance and then subtract out the displacement for thatsensor 410 under zero load. As a result, computer system 250 maydetermine just how much each sensor 410 is displaced under load. Thedisplacement of a sensor(i) may be represented by:Z _(i) =Ax _(i) +By _(i) +C,where x_(i) and y_(i) are positions of sensor(i) in the X and Y planes,respectively; A and B are displacement components due to bending; and Cis a displacement component due to tension. Computer system 250 may usea Least Mean Square process, or another process, to identify a planethrough the displacements:$E = {\sum\limits_{i = 1}^{N}\quad{\left\lbrack {Z_{i} - \left( {{Ax}_{i} + {By}_{i} + C} \right)} \right\rbrack^{2}.}}$

Once the variables A, B, and C are known, then computer system 250 maydetermine tension, bending, and orientation of bending associated withriser 130. Tension (T) may be determined based on:T=K _(axial) C,where K_(axial) may refer to a stiffness value associated with loadmeasurement unit 210. Bending (Be) may be determined based on:Be=K _(bend) {square root}{square root over (A ² +B ² )},where K_(bend) may refer to a bending stiffness value associated withload measurement unit 210. A load measurement unit 210 may be calibratedbeforehand to determine values for K_(axial) and K_(bend). Orientationof bending may be determined based on A and B (i.e., the displacementcomponents due to bending).

Computer system 250 may present information to an operator via agraphical user interface. The display parameters of the graphical userinterface may include individual sensor status, inductance, andcalculated load, tension and bending values associated with a loadcarrying member (instantaneous or averaged), and/or other informationthat may be useful to the operator.

Exemplary Processing

FIG. 8 is a flowchart of exemplary processing for determining tension,bending, and orientation of bending associated with a load carryingmember, such as a mooring 120 or riser 130, according to animplementation consistent with the present invention. Processing maybegin with the calibration of the components of signal conditioningsystem 240 (act 810). Computer system 250 may instruct signal processingsystem 240 to enter the calibration mode. Computer system 250 may theninput digitized data via the D/A channel of interface 610 andsimultaneously calibrate the components of signal conditioning system240 to determine magnitude and phase corrections for all of the channelsrelative to the reference A/D channel 0.

Thereafter, computer system 250 may instruct signal processing system240 to enter the data acquisition mode. In the data acquisition mode,sensor inductance may be determined using the voltage divider of signalconditioning system 240 (act 820). For example, the D/A channel ofinterface 610 may apply a band-limited random or sine input to the cableends through driver 630. The reference voltage input (Vi) and theresponse voltage samples (Vm) may then be measured at the A/D channelsof interface 610. Reference voltage input (Vi) may be measured at theA/D channel 0 and the reference voltage samples (Vm) may besimultaneously measured at the A/D channels 1−N.

Computer system 250 may perform a discrete Fourier transform on the dataobtained during the calibration mode and the data obtained during thedata acquisition mode at the excitation frequency. Computer system 250may divide the complex amplitude of the data from each of the channelsobtained during the data acquisition mode by the complex amplitude ofthe data from each of the channels obtained during the calibration modeto obtain a set of N complex transfer functions TF. The TF values may beused in the equation for LS (identified above) to obtain the inductanceof each sensor 410.

Once sensor inductance has been determined, sensor displacement may bedetermined (act 830). Sensor displacement may be estimated frominformation gathered during the previously-conducted sensorcalibrations. The displacements of several sensors 410 may then be usedto construct a plane through the displacements using a Least Mean Squarealgorithm, as described above. Construction of the plane may facilitatethe determination of the displacement components due to bending andtension, as described above.

Once the displacement components due to bending and tension aredetermined, the tension, bending, and orientation of bending associatedwith the load carrying member may be determined (act 840). As describedabove, the tension may be determined based on a stiffness value and thedisplacement component due to tension. As also described above, thebending may be determined based on a bending stiffness value and thedisplacement components due to bending, and the orientation of bendingmay be determined based on the displacement components due to bending.

Load Cell Configuration

Thus far, a load measurement unit has been described as the vehicle formeasuring the load associated with a load carrying member, such as amooring or riser. In an alternate implementation consistent with theprinciples of the invention, a load cell may be used. In this load cellconfiguration, one or more load cells may be associated with each loadcarrying member. Instead of being located along the periphery of theload carrying member, the load cells are connected to the load carryingmember at a point where the load carrying member connects to somethingelse, like the platform. Like the load measurement unit, the load cellsmeasure the load associated with the load carrying member.

FIG. 9 is an exemplary diagram of a sensor 900 according to animplementation consistent with the principles of the invention. Sensor900 may include a variable reluctance sensor, such as the one describedin U.S. Pat. No. 5,359,902. Sensor 900 may include a hollow cylinder 910connected to rigid end caps 920 and 930. Hollow cylinder 910 may be ofcircular cross-section and act as an elastic element for forces appliedin a direction along the axis of cylinder 910. Cylinder 910 may, forexample, be constructed of a high grade steel that has a very repeatableand essentially linear elasticity. Cylinder 910 may act essentially as alossless spring. While the spring constant will typically be very highas understood by those skilled in the art, the forces intended to bemeasured may also be quite high.

End caps 920 and 930 connect to the ends of cylinder 910. In anotherimplementation consistent with the present invention, end caps 920 and930 are not separate from, but are integral with, cylinder 910. At leastone of end caps 920 and 930 may connect to the load carrying member.

Within cylinder 910, sensor 900 may include C-shaped magnetic core 940,I-shaped magnetic core 950, brackets 960 and 970, and windings 980.C-shaped magnetic core 940 may be constructed, for example, of a highlypermeable laminated transformer material. C-shaped core 940 may bemounted on upper end cap 920 via bracket 960 with the ends of theC-shape pointed downward or in a direction generally parallel to thedirection of force within the wall of cylinder 910.

I-shaped magnetic core 950 may be constructed, for example, of a highlypermeable laminated transformer material. I-shaped magnetic core 950 maybe mounted on lower end cap 930 via bracket 970. I-shaped core 950 maybe positioned so that narrow gaps exist between each end of C-shapedcore 940 and a facing portion of I-shaped core 950. In an implementationconsistent with the principles of the invention, the widths of the gapsare small as compared with any transverse dimension of the ends ofC-shaped core 940. Further, the cross-sectional dimensions or areas ofthe ends of C-shaped core 940 may be smaller than those of the facingportion of I-shaped core 950.

A winding 980 may be mounted around each end of C-shaped core 940closely adjacent to the respective gap. Windings 980 may connect inseries so that their electromotive forces add. As will be understood bythose skilled in the art, C-shaped core 940 and I-shaped core 950 may behighly permeable and, thus, the gaps between cores 940 and 950 mayconstitute most of the reluctance in the magnetic circuit linkingwindings 980. Thus, the inductance exhibited may be directly dependenton the widths of the gaps in the direction of the magnetic flux in thegaps (i.e., the vertical direction as shown in FIG. 9).

As an axial load is applied to sensor 900, cylinder 910 compresses orexpands and the width of the respective gap between each end of C-shapedcore 940 and the adjacent portion of I-shaped core 950 reduces orincreases. As the gaps are reduced, the inductance exhibited increases.

Because the facing portion of I-shaped core 950 opposite each end ofC-shaped core 940 is broader in transverse dimensions than the facingend of the C-shaped core 940, the inductance value of sensor 900 may beinsensitive to small displacements of C-shaped core 940 in directionstransverse to the axis of cylinder 910 and to the widths of the gaps.Both of the gaps may be used in determining the value of inductance. Asa result, small increases in the length of one gap can compensate oroffset for small decreases in the length of the other gap. Accordingly,sensor 900 may be relatively insensitive to bending moments appliedthereto (i.e., around a horizontal axis perpendicular to the paper asillustrated in FIG. 9). Bending moments around the orthogonal horizontalaxis lying in the plane of the paper only produce changes in width as afunction of displacement across the surfaces of the ends of both gapsbut not changes in the average width of each gap, to a first orderapproximation.

In this load cell configuration, sensor 900 may connect to a signalconditioning system and a computer system, which may be configured andoperate similar to signal conditioning system 240 (FIG. 2) and computersystem 250 described above.

CONCLUSION

Systems and methods consistent with the present invention may provideportable signal conditioning and signal processing components forvariable reluctance load measurement. The systems and methods determineinductance and operational status of sensors used to measure the load ofa load carrying member, converts the sensor inductance intodisplacement, and performs a Least Mean Square process to identify aplane through the displacements. The systems and methods may use thisinformation to determine tension, bending, and orientation of bendingassociated with the load carrying member.

Systems and methods consistent with the principles of the invention maybe configured with a laptop computer to provide a portable loadmeasurement device or as a compact standalone device for deployment toremote areas or areas that are not easily accessible. For example, thecompact standalone device may be remotely operable and capable of beingplaced within a pressure vessel for deployment at or near the sea floor.

Further, systems and methods consistent with the present inventioninclude inexpensive circuitry that is amenable to operation on both lineAC power and DC battery power. The DC power capability makes the systemsand methods operable in the event of line voltage failure that may occurin critical situations, such as during a severe storm.

The foregoing description of preferred embodiments of the presentinvention provides illustration and description, but is not intended tobe exhaustive or to limit the invention to the precise form disclosed.Modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the invention. Forexample, while a series of acts has been described with regard to FIG.8, the order of the acts may differ in other implementations consistentwith the present invention. For another example, load forces upon theload sensors or load cells need not be vertical. The load sensors orload cells may operate in any orientation relative to Earth vertical.

No element, act, or instruction used in the description of the presentapplication should be construed as critical or essential to theinvention unless explicitly described as such. Also, as used herein, thearticle “a” is intended to include one or more items. Where only oneitem is intended, the term “one” or similar language is used. The scopeof the invention is defined by the claims and their equivalents.

1. A system that monitors a load associated with a load carrying member,a plurality of load sensing elements that monitor the load carryingmember, the system comprising: a voltage divider configured to measureinductance associated with the load sensing elements; and a computerdevice configured to: determine displacements of the load sensingelements based on the inductance associated with the load sensingelements, and determine the load associated with the load carryingmember based on the displacements of the load sensing elements.
 2. Thesystem of claim 1, wherein the voltage divider includes: a referenceresistor, and an impedance determined based on at least a resistor andan inductor corresponding to the load sensing elements.
 3. The system ofclaim 2, wherein the load sensing elements connect to the computerdevice via a plurality of cables; and wherein the impedance isdetermined further based on a resistor, a capacitor, and an inductorcorresponding to the cables.
 4. The system of claim 2, wherein theinductor corresponding to the load sensing elements includes a variableinductor with an inductance that changes based on changes indisplacement of the load sensing elements.
 5. The system of claim 1,wherein when determining the load, the computer device is configured to:identify a plane through the displacements using a Least Mean Squareprocess, and determine the load associated with the load carrying memberusing the plane.
 6. The system of claim 1, wherein the load associatedwith the load carrying member includes tension and bending associatedwith the load carrying member.
 7. The system of claim 6, wherein thetension is determined based on a stiffness value and a displacementcomponent due to tension.
 8. The system of claim 6, wherein the bendingis determined based on a bending stiffness value and one or moredisplacement components due to bending.
 9. The system of claim 6,wherein the load associated with the load carrying member furtherincludes orientation of bending associated with the load carryingmember.
 10. The system of claim 9, wherein the orientation of bending isdetermined based on a plurality of displacement components due tobending.
 11. The system of claim 1, wherein the system is a portablesystem and the computer device includes a portable computer device. 12.The system of claim 1, further comprising: a DC power supply configuredto provide power to the voltage divider and the computer device.
 13. Thesystem of claim 1, wherein the voltage divider and the computer deviceoperate in an absence of AC line voltage.
 14. A system for monitoring aload associated with a load carrying member, a plurality of load sensingmeans that monitor the load carrying member, the system comprising:means for determining inductance associated with the load sensing meansusing voltage division; means for determining displacement of the loadsensing means based on the inductance associated with the load sensingmeans; and means for determining the load associated with the loadcarrying member based on the displacement of the load sensing means. 15.A method for monitoring a load associated with a load carrying member, aplurality of sensors that monitor the load carrying member, the methodcomprising: measuring inductance associated with each of the sensorsusing voltage division; determining displacements of the sensors basedon the inductance associated with each of the sensors; and determiningthe load associated with the load carrying member based on thedisplacements of the sensors.
 16. The method of claim 15, wherein thevoltage division uses a reference resistance and an impedance that isdetermined based on at least a resistance and an inductancecorresponding to the sensors.
 17. The method of claim 16, wherein theinductance corresponding to the sensors includes a variable inductancethat changes based on changes in displacement of the sensors.
 18. Themethod of claim 15, further comprising: identifying a plane through thedisplacements using a Least Mean Square process.
 19. The method of claim18, wherein the determining the load includes: using the plane todetermine the load associated with the load carrying member.
 20. Themethod of claim 15, wherein the load associated with the load carryingmember includes tension and bending associated with the load carryingmember.
 21. The method of claim 20, wherein the tension is determinedbased on a stiffness value and a displacement component due to tension.22. The method of claim 20, wherein the bending is determined based on abending stiffness value and one or more displacement components due tobending.
 23. The method of claim 20, wherein the load associated withthe load carrying member further includes orientation of bendingassociated with the load carrying member.
 24. The method of claim 23,wherein the orientation of bending is determined based on a plurality ofdisplacement components due to bending.
 25. The method of claim 15,wherein the method is performed by a portable device.
 26. The method ofclaim 15, wherein the method is performed by a device that is powerableby DC battery power.
 27. The method of claim 15, wherein the method isperformed by a device that operates in an absence of AC line voltage.28. A portable load monitoring system that monitors a load associatedwith a load carrying member, a plurality of load sensing elements beingassociated with the load carrying member, the system comprising: avoltage divider configured to measure inductance associated with theload sensing elements; and a portable computer device configured to:determine displacements of the load sensing elements due to the loadbased on the inductance associated with the load sensing elements, anddetermine the load associated with the load carrying member based on thedisplacements of the load sensing elements.
 29. A system that monitors aload associated with a load carrying member, a plurality of load sensingelements being associated with the load carrying member, the systemcomprising: a DC power source; a voltage divider connected to the DCpower source and configured to measure inductance associated with theload sensing elements; and a computer device connected to the DC powersource and configured to: determine displacements of the load sensingelements due to the load based on the inductance associated with theload sensing elements, and determine the load associated with the loadcarrying member based on the displacements of the load sensing elements.30. The system of claim 29, wherein the DC power source includes abattery.